Polar Model Research Articles

Suppression of conductivity by 1 uc buffer layer at LAO/STO interface

The conducting properties of oxide heterointerface can be significantly affected by buffer layers, gate voltage, capping layer, etc.; sometimes, a monolayer is enough to show a drastic change in these properties. Herein, we report that the insertion of one unit-cell (uc) of CaMnO3 material as a buffer layer at conducting LaAlO3/SrTiO3 interface turns it into an insulator. The presence of MnO2-layer in CaMnO3 uc at the interface blocks the charge transfer to SrTiO3 which makes the interface conducting as explained by the polar catastrophe model. The study may help to resolve the puzzle of the origin of conductivity at oxide heterostructure interfaces.

A tractable physical model for the yeast polarity predicts epistasis and fitness.

Accurate phenotype prediction based on genetic information has numerous societal applications, such as crop design or cellular factories. Epistasis, when biological components interact, complicates modelling phenotypes from genotypes. Here we show an approach to mitigate this complication for polarity establishment in budding yeast, where mechanistic information is abundant. We coarse-grain molecular interactions into a so-called mesotype, which we combine with gene expression noise into a physical cell cycle model. First, we show with computer simulations that the mesotype allows validation of the most current biochemical polarity models by quantitatively matching doubling times. Second, the mesotype elucidates epistasis emergence as exemplified by evaluating the predicted mutational effect of key polarity protein Bem1p when combined with known interactors or under different growth conditions. This example also illustrates how unlikely evolutionary trajectories can become more accessible. The tractability of our biophysically justifiable approach inspires a road-map towards bottom-up modelling complementary to statistical inferences. This article is part of the theme issue 'Interdisciplinary approaches to predicting evolutionary biology'.

Multi-Scale Modeling of Dielectric Polarization in Polymer/Ferroelectric Composites

Ferroelectric materials are attractive fillers for polymer composites due to their high and non-linear dielectric constants. In this study, the dielectric response of the epoxy/BaTiO3 composite is obtained by a Sawyer–Tower measurement. In addition, we propose a multiscale computational approach that allows simulation of the polarization behavior of polymer/ferroelectric composites on the timescale above 100 ms, which is several orders of magnitude longer than previous studies. The model is free of ad hoc parameters and therefore can simulate the polarization characteristics from first-principles. Both in experiments and simulations, non-linear hysteresis behavior was observed in the epoxy/BaTiO3 composite even when the electric field across the BaTiO3 is more than an order of magnitude lower than the coercive field. The computational results suggested that this originates from the domain wall motion in BaTiO3. Some practical implications drawn from the computational results are discussed.

Drawing Breath

This project describes and discusses the performance piece Drawing Breath (2022), which combined ethnographic research into traditional Chinese calligraphy with experimental art practices to produce a drawn visualization of breathing. It first identifies the ways in which breathing is related to the practice and appreciation of Chinese calligraphy, then discusses other aspects of traditional Chinese writing practice relevant to issues of movement and embodiment. Notions of qi (‘breath’ or ‘energy’) and its associated meditative and physical practices are related to calligraphic mark-making, and Chinese aesthetic theories regarding ‘force’ and ‘form’ are presented in the context of Daoist ontological models of immanence, polarity and interdependent opposites. The paper concludes by reflecting on issues of cross-cultural artistic interaction and cultural appropriation, arguing that contemporary western drawing practice, especially that exploring notions of movement, embodiment and performance, benefits greatly from engaging with non-western practices and ontologies.

Design and Assessment of Bio-Inspired Antennas for Mobile Communication Systems

RF front-end system in the mobile communication system consists of an antenna, filter, and amplifier section. Now a day, there is a need to reduce the size of this RF front-end system. Here the challenge is the reduction in the size of the RF front end without degrading the performance. One way to reduce the size is by reducing the size or area of the antenna. This work proposes and simulates three Bio-inspired microstrip (BIMS) antenna designs. They are flower, Butterfly, and leaf shapes presented based on the perturbation method, Gielis super formula, and modified polar transformation models, respectively. These BIMS antennas were printed on fiberglass laminate (FR4) as substrate with a dielectric constant of εr = 4.4 and a loss tangent of 0.02. The simulation results cover parameters of the antenna, such as reflection coefficients (S11), surface current density (Jsurf), and radiation patterns. They offer a maximum gain of 14 dBi, 8 dBi, and 4dBi, respectively, and their results are compared with other works. These antennas are less in size, so they occupy less area compared to conventional rectangular or circular patch antenna, which radiates in L and S bands at different frequency ranges.

Multipolar SAFT-VR Mie Equation of State: Predictions of Phase Equilibria in Refrigerant Systems with No Binary Interaction Parameter.

An extension of the SAFT-VR Mie equation of state is proposed to predict the properties of multipolar fluids. The new model, referred to as multipolar M-SAFT-VR Mie, incorporates the general multipolar term developed by Gubbins and co-workers, which accounts for dipole-dipole, quadrupole-quadrupole, and dipole-quadrupole interactions. A modification of the third order terms in the perturbation theory results in an accurate description of the simulation data for multipolar Lennard-Jones fluids. Both the M-SAFT-VR Mie and polar soft-SAFT models are extended to account for polarizability, and a good agreement is obtained with molecular simulation data. The M-SAFT-VR Mie model is applied to refrigerant systems, and it is found that including both dipole and quadrupole moments in molecular models leads to more accurate results than using only a dipole moment. The new model provides excellent predictions of the vapor-liquid equilibria of zeotropic and azeotropic refrigerant mixtures without the need for binary interaction parameters, making it a valuable tool for formulating low-GWP working fluids.

Microlensing of the broad emission line region in the lensed quasar J1004+4112

J1004+4112 is a lensed quasar for which the first broad emission line profile deformations due to microlensing were identified. Detailed interpretations of these features have nevertheless remained controversial. Based on 15 spectra obtained from 2003 to 2018, in this work, we revisit the microlensing effect that distorts the C IV broad emission line profile in J1004+4112. We take advantage of recent measurements of the image macro-magnification ratios, along with the fact that at one epoch, image B was not microlensed, thus constituting a reference spectrum to unambiguously characterize the microlensing effect observed in image A. After disentangling the microlensing in images A and B, we show that the microlensing-induced line profile distortions in image A, although variable, are remarkably similar over a period of 15 years. We find they are characterized by a strong magnification of the blue part of the line profile, a strong demagnification of the red part of the line profile, and a small-to-negligible demagnification of the line core. We used the microlensing effect, characterized by either the full magnification profile of the C IV emission line or a set of four integrated indices, to constrain the broad emission-line region (BLR) size, geometry, and kinematics. For this purpose, we modeled the deformation of the emission lines considering three simple, representative BLR models: a Keplerian disk, an equatorial wind, and a biconical polar wind, with various inclinations with respect to the line of sight. We find that the observed magnification profile of the C IV emission line in J1004+4112 can be reproduced with the simple BLR models we considered, without the need for more complex BLR features. The magnification appears dominated by the position of the BLR with respect to the caustic network – and not by the velocity-dependent size of the BLR. The favored models for the C IV BLR are either the Keplerian disk or the equatorial wind, depending on the orientation of the BLR axis with respect to the caustic network. We also find that the polar wind model can be discarded. We measured the C IV BLR half-light radius as r1/2=2.8−1.7+2.0 light-days. This value is smaller than the BLR radius expected from the radius-luminosity relation derived from reverberation mapping, but it is still in reasonable agreement given the large uncertainties.

Extraction of diclofenac sodium from water using N-benzylethanolamine based ionic liquids: Computational and experimental approach

Despite the existence of numerous conventional wastewater treatment techniques, an efficient method for removing micropollutants remains elusive. Micropollutants (MPs)are chemicals that occur in trace amounts in the aquatic environment, which include pharmaceuticals, food additives, cosmetics, and dyes. The need to develop sustainable and cost-effective alternatives to eliminate these toxins has become a pressing issue. Recently, ionic liquids (ILs) have emerged as a potential candidate for wastewater treatment because of the ease in structure tunability and other unique chemical properties. This study aims to develop four N-benzylethanolamine based ionic liquids to eliminate diclofenac sodium, one of the top priority pharmaceutical micropollutants, from the aquatic environment. The ILs chosen were optimised with B3LYP theory and 6-311++G(d, p) basis set in Gaussian 16. Using integral equation formalism polar continuum model (IEFPCM) solvation as an aid, the interactions between the ILs and diclofenac medium were investigated. For the experimental studies, the liquid-liquid extraction (LLE) method was used, and parameters affecting extraction efficiencies (EE) such as IL concentration, rotation time, rotation speed, temperature, and equilibration time were optimised. The reusability of the best-performed IL was explored. Hydrophobicity, hydrogen bonding and π-π interactions were found to have a significant impact on the extraction efficiency of ILs.

European Winter Climate Response to Projected Arctic Sea‐Ice Loss Strongly Shaped by Change in the North Atlantic Jet

AbstractPrevious studies have found inconsistent responses of the North Atlantic jet to Arctic sea‐ice loss. The response of wintertime atmospheric circulation and surface climate over the North Atlantic‐European region to future Arctic sea‐ice loss under 2°C global warming is analyzed, using model output from the Polar Amplification Model Intercomparison Project. The models agree that the North Atlantic jet shifts slightly southward in response to sea‐ice loss, but they disagree on the sign of the jet speed response. The jet response induces a dipole anomaly of precipitation and storm track activity over the North Atlantic‐European region. The changes in jet latitude and speed induce distinct regional surface climate responses, and together they strongly shape the North Atlantic‐European response to future Arctic sea‐ice loss. Constraining the North Atlantic jet response is important for reducing uncertainty in the North Atlantic‐European precipitation response to future Arctic sea‐ice loss.

Improved Backward Smoothing—Square Root Cubature Kalman Filtering and Variable Forgetting Factor—Recursive Least Square Modeling Methods for the High-Precision State of Charge Estimation of Lithium-Ion Batteries

Accurate lithium-ion battery charge state estimation is crucial for battery management systems. Modeling of dual polarization—electrical equivalent circuit based on ternary lithium batteries as a research object, a variable forgetting factor recursive least square method is proposed for parameter identification given the insufficient tracking ability of the traditional recursive least squares method for abrupt and time-varying signals in a non- stationary environment. A backward smoothing square root cubature Kalman filtering algorithm is applied to enhance the accuracy and convergence speed of SOC estimation. The algorithm uses the square root update to ensure the numerical stability of the filtering and uses the idea of backward smoothing-forward filtering to improve the filtering accuracy on the basis of the first forward filtering. Finally, variable forgetting factor recursive least square is combined with backward smoothing square root cubature Kalman filtering to achieve the joint estimation of model parameters and state of charge, and the feasibility of the battery state of charge estimation is verified in different working conditions. The simulation results show that the variable forgetting factor recursive least square-backward smoothing square root cubature Kalman filter algorithm improves the study’s filtering accuracy and convergence speed of lithium-ion batteries.

Universal Time Variations in the Magnetosphere and the Effect of CME Arrival Time: Analysis of the February 2022 Event that Led to the Loss of Starlink Satellites

AbstractWe study Universal Time (UT) variations in the magnetospheric response to Coronal Mass Ejection (CME) impacts, using the example of the two CMEs that led to the destruction of 38 out of 49 Starlink satellites in early February 2022. We employ the Expanding‐Contracting Polar Cap model to analyze the variation in the size of the ionospheric polar caps and an eccentric dipole model of the geomagnetic field and thereby quantify the UT variations caused by the inductive effect of the diurnal motions of the geomagnetic poles in a “geocentric‐solar” frame of reference (i.e., a frame with an X axis that points from the center of the Earth to the center of the Sun). The results show that use of a quasi‐steady convection model predicts a similar global power deposition into the thermosphere as that inferred here, but does not give the same division of that power between the northern and southern hemispheres. We demonstrate that, through the combined effects of the Russell‐McPherron dipole‐tilt mechanism on solar‐wind magnetosphere coupling and of the diurnal polar cap motions in a geocentric‐solar frame, the power deposited varies significantly with the arrival UT of the CMEs at Earth. We also show that in the events of early February 2022, both CMEs arrived at almost the optimum UT to cause maximum thermospheric heating.

Evaluation of casein protein transport through surface functionized membranes using irreversible thermodynamics and concentration polarisation model

ABSTRACT Casein is an important protein in the raw milk and many approaches have been established to separate casein to make cheese. This study mainly deals with the analysis of casein protein (19 kDa, pI 4.6) transport characteristics through ultrafiltration (UF) membranes. Polysulfone (PS) based polymer membranes are used and modified with polyethylene imine (PEI), polydiallyl dimethyl ammonium chloride (PDDA) and polyacrylic acid (PAA). The fabricated membranes are characterized by contact angle and Fourier transforms infrared (FTIR) spectroscopy. The UF process was conducted with a dead-end filtration unit and the volumetric flux and transmission values are recorded and that varies with pressure and pH. The experimental results are explained using the concentration polarization and irreversible thermodynamics model. The characteristics of the transport of casein are determined from the values of the parameters such as the solute concentration near the surface of the membrane [Cm], the solute permeability [Pm], mass transfer coefficient [k], and the reflection coefficient [σ]. From the results, it is concluded that the casein transport through the UF membrane was controlled by convection with decrease in casein rejection. Although, this model predicts the transmission behavior as a function of flux and supports the experimental results for both membranes.

Physical modelling of dust polarization from magnetically enhanced radiative torque alignment in protostellar cores withpolaris

ABSTRACTMagnetic fields (B) are an important factor controlling the star-formation process. The leading method to observe B orientation is to use polarized thermal emission from aligned dust grains. In dense environments such as protostellar cores, however, dust grains may be inefficiently aligned owing to strong gas randomizations, making the use of dust polarization to trace Buncertain. The study of Hoang and Lazarian in 2016 demonstrated that grain alignment by radiative torques is enhanced if dust grains contain embedded iron inclusions. Here we extend the polaris code to study the effect of iron inclusions on grain alignment and thermal dust polarization towards a protostellar core, assuming uniform B. We found that paramagnetic grains produce a low polarization degree of $p \sim 1{{\ \rm per\ cent}}$ in the envelope and a negligible $p \ll 1{{\ \rm per\ cent}}$ in the central region owing to the loss of grain alignment. In contrast, grains with a high level of iron inclusions have perfect alignment and produce a high $p \sim 40{{\ \rm per\ cent}}$ in the envelope and a low $p \le 10{{\ \rm per\ cent}}$ in the central region. Grains with a moderate level of iron inclusions induce the polarization flipping from P ‖ B at millimetre to P ⊥ B at submillimetre wavelengths owing to the change in the internal alignment caused by slow internal relaxation. The weak alignment of very large grains with $a \ge 10\, {\mu \rm {m}}$ reduces dichroic extinction efficiency at submillimetre wavelengths. We found a positive correlation between p and the level of iron inclusions, which introduces a new option to constrain the abundance of solid iron locked in dust through dust polarimetry.

Radiative Effects and Costing Assessment of Arctic Sea Ice Albedo Changes

The rapid loss of Arctic Sea ice cover and thickness diminishes the surface albedo, which increases the ocean’s absorption of solar heat and exacerbates the Arctic amplification effect. According to the most recent research from the Intergovernmental Panel on Climate Change, the Sixth Assessment Report (IPCC, AR6), the extent of summer sea ice is anticipated to decrease below 1 million km2 by the 2050s as a result of the extreme climate. Nevertheless, past and future changes in sea ice albedo radiative forcing and the resulting economic cost remain to be explored in systematic and multi-disciplinary manners. In this study, we first analyze the evolution of Arctic sea ice radiative forcing (SIRF) from 1982 to 2100 using a radiative kernel method based on albedo data from the Polar Pathfinder-Extent (APP-x) and Coupled Model Intercomparison Project 5 (CMIP5). Then, the SIRF is converted to CO2 equivalent emissions via the Dynamic Integrated Model of Climate and Economy (DICE) model. Finally, the associated costs are calculated using the substitute cost method, based on the social cost of carbon to achieve the Paris Agreement targets. The results show that the average Arctic SIRF was −0.75 ± 0.1 W·m−2 between 1982 and 2020, and increased by 0.12 W·m−2 during this period. The SIRF in April–June accounts for nearly 77% of the average annual value, with a maximum absolute value of –3.2 W·m−2 in May. Through model transformation, it is shown that the Arctic SIRF rising leads to global warming comparable to the effect of an increase of 34.5 Gt of CO2 in the atmosphere relative to pre-industrialization, and results in a loss of 24.4–48.8 trillion USD for climate regulation service (CRS). From 2020 to 2100, in the representative concentration pathway (RCP) 8.5, the Arctic SIRF is projected to increase by 0.31 W·m−2. Combined with the discount rate, the estimated average annual cost over the period ranges from 6.7–13.3 trillion USD. These findings provide a systematic understanding of the radiative effect of Arctic sea ice change on the global climate and the corresponding economic cost.

Comet 19/P Borrelly in 2021–22: Change in the spin axis orientation versus previous apparitions

Comet 19P/Borrelly is characterized by the presence of a prominent polar jet that is nearly aligned with its rotation axis. The polar jet model has therefore been used in the past by several authors to determine the orientation of the comet's spin axis. To verify whether the spin axis during the 2021–22 apparition was in the expected positions according to the published pole coordinates, the position angles (PA) of the polar jet were accurately measured, resulting in a spin axis orientation at RA = 206.1° and Dec = −5.0°. These coordinates are different from all those published by other authors during previous apparitions. The comparison of the measurements of the PAs of the jet made by other authors during earlier apparitions (1911–1932 and from 1994 to 2008) with the hypothetical PAs calculated according to the new pole coordinates showed significant differences, thus confirming that the comet's axis is currently pointing to a different position. The lack of suitable images of the last perihelion passage of 2015 does not allow to clarify whether the shift of the spin axis observed in 2021–22 occurred during this orbit or is the result of a slow, secular drift or of a precession.

Changes in Winter Temperature Extremes From Future Arctic Sea‐Ice Loss and Ocean Warming

AbstractObserved rapid Arctic warming and sea‐ice loss are likely to continue in the future, unless and after greenhouse gas emissions are reduced to net‐zero. Here, we examine the possible effects of future sea‐ice loss at 2°C global warming above pre‐industrial levels on winter temperature extremes across the Northern Hemisphere, using coordinated experiments from the Polar Amplification Model Intercomparison Project. 1‐in‐20‐year cold extremes are simulated to become less severe at high‐ and mid‐latitudes in response to Arctic sea‐ice loss. 1‐in‐20‐year winter warm extremes become warmer at northern high latitudes due to sea‐ice loss, but warm by less than cold extremes. We compare the response to sea‐ice loss to that from global sea surface temperature (SST) change also at 2°C global warming. SST change causes less severe cold extremes and more severe warm extremes globally. Except northern high latitudes, the response to SST change is of larger magnitude than that to Arctic sea‐ice loss.

Carrier Capture Dynamics of Deep-Level Defects in Neutron-Irradiated Si With Improved Intracascade Potential

Defect–carrier interactions, especially carrier capture of defects (defect charging), are crucial for understanding displacement damage and failure mechanisms of semiconductor devices under irradiation. A multiscale model is thus developed to study the charging behaviors of deep-level defects in neutron-irradiated semiconductors. The model combines Monte Carlo and object kinetic Monte Carlo (OKMC) simulations for defect annealing, with improved rate equations based on the Shockey–Read–Hall (SRH) theory for defect charging. Especially, the rate equations newly include the improved intracascade electrostatic potential without adjustable parameters, acquired via a proposed effective polarized region model with annealed defect distributions. This model is applied to simulate the collector of the 2N2222 n-p-n silicon (Si) bipolar transistor under pulse-neutron irradiation. We found that the decrease in electron density under irradiation results from both the reduction of effective dopant concentration and the indirect electron trapping of stable vacancy–oxygen pairs (VO) and divacancies (V2). Moreover, two important mechanisms are revealed, including the cocharging of both V2(=/−) and VO(−/0) at 130 K, which corrects the traditional knowledge of single charging of V2(=/−) and the suppressed occupation of V2(=/−) due to the intracascade electrostatic potential formed by V2(−/0) charging. It is very helpful to understand the key mechanisms of the defect–carrier interactions and resolving performance failures of neutron-irradiated semiconductors.

SN 2020uem: a Possible Thermonuclear Explosion within a Dense Circumstellar Medium (II). The Properties of the CSM from Polarimetry and Light-curve Modeling

Type IIn/Ia-CSM supernovae (SNe IIn/Ia-CSM) are classified by their characteristic spectra, which exhibit narrow hydrogen emission lines originating from strong interaction with a circumstellar medium (CSM) together with broad lines of intermediate-mass elements. We performed intensive follow-up observations of SN IIn/Ia-CSM 2020uem, including photometry, spectroscopy, and polarimetry. In this paper, we focus on the results of polarimetry. We performed imaging polarimetry at 66 days and spectropolarimetry at 103 days after discovery. SN 2020uem shows a high continuum polarization of 1.0%–1.5% without wavelength dependence. Besides, the polarization degree and position angle keep roughly constant. These results suggest that SN 2020uem is powered by strong interaction with a confined and aspherical CSM. We performed simple polarization modeling, based on which we suggest that SN 2020uem has an equatorial-disk/torus CSM. Besides, we performed semi-analytic light-curve modeling and estimated the CSM mass. We revealed that the mass-loss rate in the final few hundred years immediately before the explosion of SN 2020uem is in the range of 0.01–0.05 M ⊙ yr−1, and that the total CSM mass is 0.5–4 M ⊙. The CSM mass can be accommodated by not only a red supergiant (RSG), but also by a red giant (RG) or an asymptotic giant branch (AGB) star. As a possible progenitor scenario of SN 2020uem, we propose a white dwarf binary system including an RG, RSG, or AGB star, especially a merger scenario via common envelope evolution, i.e., the core-degenerate scenario or a variant.

UAV-Correlated MIMO Channels: 3-D Geometrical-Based Polarized Model and Capacity Analysis

The unmanned aerial vehicle (UAV) communication with the multiple-input–multiple-output (MIMO) system has attracted lots of attention to improve spectral efficiency and channel capacity. The large antenna spacing is often required to reduce the spatial correlation between subchannels. However, this requirement cannot be well satisfied in practical scenarios due to the limited dimension of UAV platforms. Therefore, polarization diversity is a promising approach for UAV MIMO systems. In this work, we propose a three-dimensional (3-D) geometrical-based polarized model for UAV-correlated MIMO channels. By utilizing the geometrical theory of polarization, we describe the channel depolarization caused by the terrestrial scattering environment based on the multicylinder geometrical model and then acquire the channel polarization function and polarized channel impulse response (CIR). Furthermore, we investigate the impact of the key factors, such as the UAV tilt rotation, cross-polarization, and limited antenna spacing on the UAV MIMO channel capacity. To validate the proposed UAV channel model, we compare the spatial correlations of the numerical simulation and UAV field measurement results for the co- and cross-polarized channels, and the close agreements between them are observed. This work can provide useful guidance and support for the design and performance evaluation of UAV communication networks.

Precipitation trends (1958–2021) on Ammassalik island, south-east Greenland

Along with Arctic warming, climate models project a strong increase in Arctic precipitation in the 21st century as well as an increase in the ratio of liquid to total precipitation. In the precipitation-rich region of south-east Greenland, precipitation changes could locally have significant impacts on runoff. However, climate data are sparse in this remote region. This study focuses on improving our understanding of the past precipitation changes on Ammassalik island in south-east Greenland between 1958 and 2021. To assess past changes in air temperature at 2-meter and precipitation, output from a regional polar climate model (RACMO2.3p2) is evaluated with measurements from automatic weather stations in Tasiilaq and on Mittivakkat glacier. In addition, RACMO2.3p2 is used to assess past seasonal changes in air temperature at 2-meter, precipitation amount, precipitation phase and the altitude of the rain/snow boundary. We find that the climate model accurately represents the monthly average observed air temperature at 2-meter. While total precipitation is overestimated, interannual variability of precipitation is properly captured. We report a significant increase of summer temperature at 2-meter of +0.3°C/decade (p<0.01) at Mittivakkat glacier and +0.2°C/decade (p<0.01) in Tasiilaq in 1958–2021. For the subperiod 1990–2019, the trend in annual averages of temperature at 2-meter in Tasiilaq (+0.8°C/decade, p=0.02) corresponds well to known temperature trends on the Greenland Ice Sheet within the same period. On Mittivakkat glacier a significant trend is not detected within this subperiod (+0.2°C/decade, p=0.25). The modelled liquid precipitation ratio on Ammassalik island increased in all summer months (1958–2015) by +2.0/+1.9/+1.8%/decade in June/July/August respectively. In July and August, these trends were stronger at higher elevations. No statistical evidence is found for trends in other seasons. We also identify monthly increases in the altitude of the rain-to-snow boundary (+25/+23/+20 m/decade in July/August/September respectively).